Figuring out how much torque I need

[Daftlander]

I'm building a computer controlled camera head, so I need a stepper motor. But I haven't got the foggiest of which one to buy or how to do the calculations to figure that out. 

 

I'm trying to turn a load of two kilos around an axis. I'm also using a worm drive so that I can reduce backlash. 

 

What other information do I need? Which calculations do I need to do? I'm kind of lost. 

[Enderman]

If the load is balanced around the axis and you're using ball bearings then you need close to 0 torque to move it, more torque will just mean that it moves faster.

[Daftlander]

This may sound like a stupid question, but what do you mean by "balanced around the axis".

[HolaImBob]

i think he means for the centre of gravity to be very close to the centre of the axis. so in the picture below where the red is would be the centre of gravity around the axis or you could say its balanced around the axis.

[Daftlander]

Thanks. I thought that's what it was. But you can never be too careful.

[straight_stewie]

On 12/19/2018 at 5:22 PM, Daftlander said:

but what do you mean by "balanced around the axis".

Bear in mind that the geometric center of the camera might not be coincident with the center of gravity of the camera, especially if you are using a long lens. If using very long telescopic lenses and needing quick, accurate movement to track moving targets, this could become a concern.

Do you plan on tracking relatively fast moving objects with a large lens, or are you taking mostly stills?

[James Evens]

M=r x F is the formula (M,r and F are vectors) to get the torque the camera is creating during rotation. You also need to add friction loses.

Pls don't mount the camera without additional support to the motor shaft unless you know the motor supports this weight/force.

[Daftlander]

On 12/20/2018 at 11:33 PM, straight_stewie said:

Do you plan on tracking relatively fast moving objects with a large lens, or are you taking mostly stills?

It's for stills and with a relatively short prime lens.

 

Sorry I abandoned this thread for so long. It has been a marathon couple of weeks at work.